Mold board for earthmoving scraper



2 Sheets-Sheet 1 Filed April 5, 1951 V" ilul IN V EN TOR. 19065 M. SMITH 6/ 47 7 ATTORNEY NOV. 1, M SMITH MOLD BOARD FOR EARTHMOVING SCRAPER 2 Sheets-Sheet 2 Filed April 3, 1951 ATTORNEY United. States Patent MOLD BOARD FOR EARTHMOVING SCRAPER Roger M. Smith, Mossville, Ill., assignor to Caterpillar Tractor (30., Peoria, Ill., a corporation of California Application April 3, 1951, Serial No. 218,996

1 Claim. (Cl. 37-141) This. invention relates to self-loading earthmoving scrapers in general and more particularly to means for guiding the flow of incoming material during loading to reduce the power required to obtain a full load.

One type of self-loading scraper now commonly employed for collecting and moving large quantities of earth or like material comprises a large bowl supported on ground engaging wheels and having a draft connection by mean of which it is connected to and drawn by a tractor unit. The bowl is usually provided with a scraping edge adjacent its forward portion which is adapted to be lowered into scraping contact with the earth to effect collection of the earth which is deposited in the bowl. The rear of the bowl is closed by an ejector adapted for forward sliding movement to empty the bowl of its contents, and the front is provided with a gate-like device or apron which, although normally open during loading and unloading operations, may be swung downwardly or closed during transportation of a load of earth. The scraper bowl, ejector, and apron are actuated by means such as hydraulic jacks or by cables wound upon drums carried by the tractor. When cables are used the cable winding drums are powered for rotation, through suitable power take-ofls from the tractor, to take in or pay out cable at the control of the tractor operator.

In this kind of scraper, loading is accomplished by lowering the forward edge of the bowl into scraping contact with the earth which is directed upwardly into the bowl, as the scraper is drawn forwardly by the tractor. During the early part of the loading cycle, the power required to draw the scraper forwardly is relatively small but increases rapidly as the bowl is filled due to friction between the material already in the bowl and the incoming material. As a result, to completely fill the scraper bowl, it is necessary either to employ a much more powerful tractor than would normally be required for transporting the loaded scraper from one location to another, or utilize a booster tractor to help push the scraper during loading.

It is, therefore, an object of the present invention to provide an earthmoving scraper having means for reducing the power required for loading by reducing the friction between the material already in the scraper bowl and the incoming material. Other objects and advantages of the present invention will be made apparent in the following specification wherein reference is made to the accompanying drawing.

In the drawings:

Fig. l is a view in side elevation of an earth-moving scraper embodying the present invention with parts in section to more clearly illustrate its construction;

Fig. 2 is a schematic diagram of a conventional scraper during the early part of the loading cycle illustrating the path of the incoming material;

Fig. 3 is a view like Fig. 2 illustrating the path of the incoming material during the final stages of the loading operation; and

Fig. 4 is a view like Fig. 2 of a scraper embodying the 2,722,065 Patented Nov. 1, 1955 present invention illustrating the improved path and action of the incoming material.

In Fig. 1, an earthmoving scraper of the type in which the present invention is used is illustrated as comprising an earth receiving bowl 10 having side plates only one of which is shown at 11 and a bottom 12 which, at its forward edge, is provided with a cutting edge 13. The bowl is supported adjacent its rear end by a pair of ground engaging wheels 14, and at its forward end by a draft frame 16 supported on ground engaging wheels 17. The draft frame is provided with a pair of arms 18 which are pivotally connected to the side plates of the bowl by pins, only one of which is indicatedat 19 to form a hinged connection allowing the bowl to be lowered into scraping contact with the earth. The rear of the bowl is closed by an ejector plate 21 adapted to be moved forwardly to discharge the bowl contents, and the front is closed by an apron 22 pivotally secured as at 23 from the sides of the scraper bowl to permit raising during loading and unloading operations.

Although it is not shown, the scraper is adapted to be connected to and drawn by a tractor or like draft vehicle. The scraper bowl, apron, and ejector are actuated in a conventional manner by cables 24 extending forwardly to cable winding drums not shown but carried on the tractor. The cable winding drums are powered for rotation through a suitable power take-off from the tractor to take in or pay out on the cables at the control of the operator.

In operation, the scraper is loaded by partially opening the apron and lowering the bowl, bringing its forward edge into scraping engagement with the earth. As is best illustrated in Figs. 2 and 3, during forward movement of the scraper, a column of material indicated at 26 is sheared from the surface of the earth and is directed into the bowl by the cutting edge. As material is collected in the bowl, it is necessary for the incoming material to force its way upwardly through the material already collected as is illustrated in Fig. 3. Due to friction between the incoming column of material and the material already in the bowl, the power requirements for drawing the scraper forward at a uniform rate increases substantially as the bowl is filled.

Due to the physical properties of soils, the friction forces opposing the entrance of the incoming column of material is a function of the angle of the column with respect to the vertical and decreases as the angle ap proaches the vertical. As a result, the natural tendency of the incoming column of material is to gradually bend from its entering angle, the initial position of which is somewhat as shown in Fig. 2, toward a path which more nearly approaches a vertical column as illustrated in Fig. 3. This bending movement results from considerable force acting on the rear face of the column which, in turn, materially increases the frictional force resisting movement of the column.

The friction forces opposing movement of the column of earth entering the scraper bowl may be materially decreased by the provision of a guide plate or mold board illustrated at 27 in Figs. 1 and 4. The mold board forms a continuation of the cutting edge and is curved to bend the incoming column of earth toward a substantially vertical path and is made of steel which becomes polished in use so as to acquire a relatively low co-efiicient of friction with earth-like materials. By providing a surface having a low co-eflicient of friction to bend the column of incoming material toward a vertical path, the frictional forces are materially reduced, and the power required to load the scraper is correspondingly reduced.

The mold board is connected to the ejector for movement therewith as by spaced push arms 28 which at their rear ends are secured by bolts 29 to the ejector plate 21.

Thus, during unloading of the scraper, the mold board is moved forwardly with the ejector out of the path of the material discharged from the scraper bowl. The apron will, of course, have been raised to an open position prior to the ejecting operation. During this forward movement of the ejector the material in the bowl will discharge over the cutting edge 13 being free to pass through the space between the push arms 28 and behind the mold board 27.

The principal advantage of the present invention is that it reduces the power necessary to load a scraper. Hence a larger scraper may be employed or a smaller draft vehicle may be used with the same scrapper as the greatest power is required during the latter part of the loading operation so that there is always an excess of power over that actually required for transporting the loaded scraper and discharging its contents.

I claim:

In an earthmoving scraper which comprises a bowl supported to be advanced over the ground, a cutting edge secured to the bowl and engageable with the ground to dislodge earth and direct it into the bowl, and ejector disposed in and normally supported adjacent the rear portion of the bowl, and means to advance the ejector forwardly in a substantially horizontal path through the bowl to discharge the contents thereof, a guide plate in the bowl adjacent the cutting edge for guiding earth entering the bowl, and a pair of spaced push arms connecting the guide plate with the ejector and supporting the guide plate whereby it will be moved forwardly and away from the cutting edge when the ejector is advanced.

References Cited in the file of this patent UNITED STATES PATENTS 2,179,532 Walch Nov. 14, 1939 2,207,424 Wood July 9, 1940 2,229,103 Le Tourneau Jan. 21, 1941 2,243,831 Berner June 3, 1941 2,250,289 Barrett July 22, 1941 2,257,761 Pa-ulsen Oct. 7, 1941 

